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Abstract:

In various embodiments, a booster antenna structure for a chip card is
provided, wherein the booster antenna structure may include a booster
antenna; and an additional electrically conductive structure connected to
the booster antenna.

Claims:

1. A booster antenna structure for a chip card, wherein the booster
antenna structure comprises: a booster antenna; and an additional
electrically conductive structure connected to the booster antenna.

2. The booster antenna structure as claimed in claim 1, wherein the
booster antenna and the additional electrically conductive structure
jointly form an arrangement which has a resonant frequency of
approximately 13.56 MHz.

3. The booster antenna structure as claimed in claim 1, wherein the
additional electrically conductive structure has a meander structure.

4. The booster antenna structure as claimed in claim 1, wherein the
additional electrically conductive structure has an ohmic impedance of at
least 5 Ω.

5. The booster antenna structure as claimed in claim 1, wherein the
additional electrically conductive structure and the booster antenna are
formed from different materials.

6. The booster antenna structure as claimed in claim 1, wherein the
additional electrically conductive structure and the booster antenna are
coupled to one another in series.

7. The booster antenna structure as claimed in claim 1, wherein the
additional electrically conductive structure and the booster antenna are
coupled to one another in parallel.

8. The booster antenna structure as claimed in claim 1, wherein the
booster antenna has at least one inductive coupling area.

9. The booster antenna structure as claimed in claim 1, wherein the
booster antenna structure further comprises a capacitor.

10. The booster antenna structure as claimed in claim 9, wherein the
capacitor is formed as a plate capacitor.

11. The booster antenna structure as claimed in claim 9, wherein the
capacitor has a number of lines arranged next to one another in parallel,
wherein every second line is connected to the same capacitor electrode.

12. The booster antenna structure as claimed in claim 9, wherein
structures which form the capacitor, and the booster antenna structure,
are arranged in the same plane.

13. A contactless chip card module arrangement, comprising: a booster
antenna structure for a chip card, wherein the booster antenna structure
comprises: a booster antenna; and an additional electrically conductive
structure connected to the booster antenna; a contactless chip card
module which comprises: a chip; and a coil which is coupled electrically
to the chip; wherein the booster antenna structure is coupled inductively
to the coil of the contactless chip card module by means of at least one
inductive coupling area of the booster antenna.

14. The contactless chip card module arrangement as claimed in claim 13,
wherein the booster antenna structure is power-matched to the contactless
chip card module; and wherein the power matching is adjustable by means
of the additional electrically conductive structure.

15. The contactless chip card module arrangement as claimed in claim 13,
wherein the at least one inductive coupling area of the booster antenna
has a structure enclosing the coil of the contactless chip card module.

16. The contactless chip card module arrangement as claimed in claim 15,
wherein the enclosing structure has at least one turn which encloses the
coil of the contactless chip card module.

17. The contactless chip card module arrangement as claimed in claim 13,
wherein the at least one inductive coupling area of the booster antenna
is arranged in a corner area of the booster antenna.

18. The contactless chip card module arrangement as claimed in claim 13,
wherein the at least one inductive coupling area of the booster antenna
is located within an area which is bounded by conductor tracks forming
the booster antenna.

19. The contactless chip card module arrangement as claimed in claim 13,
wherein the at least one inductive coupling area of the booster antenna
is located outside an area which is bounded by conductor tracks forming
the booster antenna.

20. The contactless chip card module arrangement as claimed in claim 13,
wherein the contactless chip card module also has chip card contacts
which are configured for providing a contact-based chip card interface.

22. A contactless chip card module arrangement, comprising: a booster
antenna structure for a chip card, wherein the booster antenna structure
comprises: a booster antenna; and an additional electrically conductive
structure connected to the booster antenna; a contactless chip card
module which comprises: a chip; and a coil which is coupled electrically
to the chip; wherein the booster antenna structure is coupled inductively
to the coil of the contactless chip card module; wherein the electrically
conductive structure external to the booster antenna has an ohmic
impedance, the value of which results from an operating frequency of the
chip, the inductance of the booster antenna and the quality factor of the
booster antenna.

23. The contactless chip card module arrangement as claimed in claim 22,
wherein the contactless chip card module also has chip card contacts
which are configured for providing a contact-based chip card interface.

Description:

[0001] This application claims priority to German Patent Application
Serial No. 10 2011 056 323.7, which was filed Dec. 13, 2011, and is
incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] Various embodiments relate to a booster antenna structure for a
chip card.

BACKGROUND

[0003] In the case of normal chip cards which are widely used, for example
in electronic payment transactions, the communication between the chip
located on the chip card and a reader is contact-based, i.e. via chip
card contacts exposed toward the outside of the chip card. For this
purpose, however, the chip card must always be singled out when used and
introduced into a corresponding reader which may be considered to be
disruptive by a user. An interesting extension which solves the problem
is offered by so-called dual interface chip cards in which the chip can
also communicate by means of a contactless interface in addition to the
normal contact-based interface. The contactless interface on the chip
card can have a chip card antenna which is contained in the chip card and
connected to the chip. The chip card antenna and the chip can be arranged
conjointly on a chip card module wherein such a miniaturized form of the
chip card antenna can then be called a chip card module antenna.
Independently of the type of chip card antenna, an electrical connection
is formed between it and the chip card module or the chip, respectively.

[0004] In the case of electronic payment systems, for example, a
functional distance of up to 4 cm is required between the chip and the
reading unit. However, meeting this target specification may be found to
be problematic since it may not be possible in some cases to arrange a
sufficiently large chip card module antenna on the small surface
available on the chip card module for wireless communication to take
place at the required distance. In order to improve the wireless
communication capability, a further antenna can be provided in addition
to the chip card module antenna, namely an amplifier antenna or booster
antenna. The booster antenna can be provided on a separate layer and
contained in the chip card. The separate layer which contains the booster
antenna can be laminated into the chip card, for example, during its
production.

[0005] In the case of chip card antennas which are not arranged on the
chip card module and therefore have in most cases an adequate size, the
use of a booster antenna can be omitted. When completed chip card bodies
are equipped with chip card modules, however, the chip card must then be
milled precisely so that the contacts provided on the chip card module
can be positioned over corresponding contacts of the chip card antenna.
The contacts can then be joined together by means of an adhesive,
supplying pressure.

[0006] The production process described above is costly and complex. In
addition, the contact locations between chip card module and the chip
card antenna can have little mechanical ruggedness and may become
detached in the case of bending and folding processes to which chip cards
can be exposed in everyday use. Having regard to these problems, the
expected life of a chip card having a chip card antenna may be two years.
In general, a far longer life of, for example, ten years would be
desirable, for instance when such chip cards are used in governmental
facilities where the costs of exchanging or renewing due to the volume of
chip cards used could be saved.

[0007] To avoid the problems of the mechanically susceptible electrical
connection with the chip card module or the chip, respectively, existing
in the case of large-format chip card antennas, booster antennas are
coupled inductively to chip card module antennas. Normal booster antennas
extend in most cases over the entire surface of the chip card, if
necessary also over part-areas which are provided, for example, for
lettering embossed in the chip card (embossing areas, defined, for
example, in ISO/IEC 7811-1 Standard) or are provided for the chip cavity
so that such chip cards are basically not ISO/IEC-compliant. Furthermore,
there has hitherto not been any optimization of the booster antenna in
chip cards with regard to their electrical parameters so that such chip
cards cannot be certified, for example, according to the EMVCo
Standard--a global standard for credit and ATM cards on the basis of chip
card technology.

SUMMARY

[0008] In various embodiments, a booster antenna structure for a chip card
is provided, wherein the booster antenna structure may include a booster
antenna; and an additional electrically conductive structure connected to
the booster antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In the drawings, like reference characters generally refer to the
same parts throughout the different views. The drawings are not
necessarily to scale, emphasis instead generally being placed upon
illustrating the principles of the invention. In the following
description, various embodiments of the invention are described with
reference to the following drawings, in which:

[0011] FIG. 2A shows a transmission system having a reading unit and a
chip card module with chip card module antenna without booster antenna
structure;

[0012] FIG. 2B shows a transmission system having a reading unit and a
chip card module with chip card module antenna and with a booster antenna
structure according to various embodiments;

[0013] FIG. 3 shows a diagram for illustrating the influence of the number
of turns of the booster antenna structure according to various
embodiments on the voltage induced in the chip card module antenna;

[0014] FIGS. 4A to 4F show various contactless chip card module
arrangements for forming the inductive coupling area according to the
various embodiments;

[0015] FIG. 5 shows a section of an embodiment of an inductive coupling
area;

[0016] FIG. 6 shows a diagram for illustrating the dependence of a
coupling factor on the distance between turns of the chip card module
antenna and booster antenna turns;

[0017] FIG. 7 shows a section of a booster antenna structure according to
various embodiments;

[0018] FIG. 8A shows a section of a contactless chip card module
arrangement according to various embodiments;

[0019] FIG. 8B shows a section of a further contactless chip card module
arrangement according to various embodiments;

[0020] FIG. 9 shows a circuit diagram of a system of reading unit and a
contactless chip card module arrangement according to various
embodiments;

[0021] FIG. 10 shows a circuit diagram of a system of a contactless chip
card module arrangement according to various embodiments;

[0022] FIG. 11A shows a booster antenna structure according to various
embodiments with a finger capacitor;

[0024] FIG. 12A shows a booster antenna structure according to various
embodiments with a spiral capacitor;

[0025] FIG. 12B shows a booster antenna structure according to various
embodiments with a dummy turn as capacitor;

[0026] FIG. 13A shows a top of a booster antenna structure according to
various embodiments;

[0027] FIG. 13B shows a bottom of a booster antenna structure according to
various embodiments;

[0028] FIG. 13C shows an overlaid view of the top of the booster antenna
structure from FIG. 13A and the bottom of the booster antenna structure
from FIG. 13B;

[0029] FIG. 14 shows an image of a booster antenna structure, produced by
means of an electroplating process, according to various embodiments; and

[0030] FIG. 15 shows an image of a booster antenna structure, produced by
means of an etching process, according to various embodiments.

DESCRIPTION

[0031] The following detailed description refers to the accompanying
drawings that show, by way of illustration, specific details and
embodiments in which the invention may be practiced.

[0032] The word "exemplary" is used herein to mean "serving as an example,
instance, or illustration". Any embodiment or design described herein as
"exemplary" is not necessarily to be construed as preferred or
advantageous over other embodiments or designs.

[0033] The word "over" used with regards to a deposited material formed
"over" a side or surface, may be used herein to mean that the deposited
material may be formed "directly on", e.g. in direct contact with, the
implied side or surface. The word "over" used with regards to a deposited
material formed "over" a side or surface, may be used herein to mean that
the deposited material may be formed "indirectly on" the implied side or
surface with one or more additional layers being arranged between the
implied side or surface and the deposited material.

[0034] In the detailed description which follows, reference is made to the
attached drawings which form a part of it and in which, for the purpose
of illustration, specific embodiments are shown in which the invention
can be exercised. In this regard, directional terminology such as, for
instance, "top", "bottom", "front", "rear", etc. are used with reference
to the orientation of the figure(s) described. Since components of
embodiments can be positioned in a number of different orientations, the
directional terminology is used for illustration and is in no way
restrictive. Naturally, other embodiments can be used and structural or
logical changes can be performed without deviating from the range of
protection of the present invention. Naturally, the features of the
various embodiments described herein can be combined with one another
unless specified differently specifically. The detailed description which
follows should, therefore, not be considered in a restrictive sense and
the protective range of the present invention is defined by the attached
claims.

[0035] Within the framework of the present description, the terms
"linked", "connected" and "coupled" are used for describing both a direct
and an indirect link, a direct or indirect connection and a direct or
indirect coupling. In the figures, identical or similar elements are
provided with identical reference symbols as far as this is appropriate.

[0036] FIG. 1 shows a section of a rear of a chip card module 100
including a chip card module antenna with which a booster antenna
structure according to various embodiments may be coupled. The rear of
the chip card module 100 may be understood to be the side which is
arranged opposite the side of the chip card module on which the chip card
contacts are arranged and is thus not visible from the outside after
insertion of the chip card module into a chip card body. The chip card
module 100 has a carrier 112 on which an integrated circuit in the form
of the chip 102 is arranged. As in the embodiment of the chip card module
100 shown, the carrier 112 may be at least partially transparent so that
the chip card contacts 114 which are arranged on the front of the carrier
112 are also visible from the rear of the chip card module 100. The chip
card contacts 114 are coupled to the chip 102 by means of wiring 110. At
the rear of the carrier 112 an off-chip coil 104 is provided and has
thirteen turns in the present embodiment. The turns of the off-chip coil
104 are arranged in a ring around the chip 102. Each of the coil turns
has an almost square or rectangular shape with rounded corners, the
left-hand side having in the present embodiment a kink 116, i.e. a course
deviating from a straight line. The kink 116 has the effect that the coil
turns are offset toward the center of the off-chip coil 104 and thus an
area is created at the outer edge of the coil 104 at which, for example,
an end contact 106 of the coil may be arranged. The design of the
off-chip coil 104 may be adapted to other components present on the
carrier 112 as required. The shape of the coil turns may naturally
deviate from the shape shown in FIG. 1 and have, for example, other
kinks. The off-chip coil 104 has at its outer end the end contact 106.
The end contact 106 is conducted to the front of the carrier 112 by means
of a passage and is connected to a contact bridge 118. The contact bridge
118, which is arranged on the front of the carrier 112, is coupled to a
further passage which is connected to a further contact 108 which, in
turn, is coupled to the chip 102. In this manner, the off-chip coil 104
may be closed without an additional plane having to be built up on the
rear of the carrier 112 in which a line could run which crosses the coil
turns. The off-chip coil 104 shown in FIG. 1 is a unilateral module
antenna, wherein a contact bridge 118 is used on the side of the chip
card contacts 112 in order to close the off-chip coil 104. The chip 102
arranged on the carrier 112 may have, for example, an internal capacitor
of approximately 40 pF to 100 pF, for example in the range of about 50 pF
to 80 pF. The turns of the off-chip coil 104 may have, for example,
silver, aluminum, copper, gold and/or conductive alloys and may have a
conductor track width of at least 40 μm which can be, for example,
about 60 μm, about 80 μm or about 100 μm or about up to 200
μm. The turns of the off-chip coil 104 may be arranged, for example,
at a distance of about 80 μm from one another on the carrier 112. Both
parameters--conductor track width and conductor track spacing--are
parameters which can be adapted with regard to the inductance of the
off-chip coil 104 to be achieved.

[0037] The chip card module 100 shown in FIG. 1 is a so-called CoM (coil
on module) which has the chip and a coil, the coil handling the function
of an antenna and providing for contactless communication between the
chip and a reading unit. The chip card module 100 may be a dual interface
chip card module so that the chip can communicate with a reading unit by
means of a contact-connected interface (by means of contacts 114) and by
means of a contactless interface (off-chip coil 104). The contactless
chip card module according to various embodiments, for example a
contactless chip card module of a dual interface chip card, has a
resonant circuit which may essentially have the chip and the off-chip
coil and can be operated independently. The resonant frequency of the
resonant circuit ay be set to the operating frequency of the chip in this
arrangement and be, for example, approximately 13.56 MHz, this frequency
corresponding to one of the frequencies of the RFID (radio-frequency
identification) standard in the short-wave band.

[0038] FIG. 2A shows a system 200 of reading unit 202 and chip card module
206 with chip card module antenna, but without booster antenna structure.
The contactless communication (often also called near-field
communication) between reading unit 202 and chip card module 206 is based
on electromagnetic waves (for example on one or more magnetic fields),
wherein an antenna 204 of the reading unit 202, which can be constructed
as a coil, and the off-chip coil arranged on the chip card module 206 are
used for transmitting these. In the transmission of signals between
reading unit 202 and chip card module 206, a current flow is induced in
the chip card module antenna of the chip card module 206 by a clocked
magnetic field of the reading unit 202. In the chip card module 206, a
load resistance is switched on and off at the clock rate of the signal,
which is to be transmitted. This load modulation causes a change in the
current flow through the chip card module antenna, which in turn results
in a changing reaction of the chip card module antenna to the amplitude
of the magnetic field of the reader 202. The modulation of the magnetic
field of the reader, caused by the load modulation in the chip card
module, can be detected in the reader. In order to improve the
performance of the contactless communication of a chip card module, an
amplifier antenna (also called booster antenna) can be coupled
additionally to the chip card module. FIG. 2B shows a system 220 of
reading unit 202 and chip card module 206 with chip card module antenna
and with booster antenna structure 208 according to various embodiments.
The booster antenna structure 208 acts as an amplifying intermediary, as
it were, between the antenna 204 of the reading unit 202 and the off-chip
coil of the chip card module 206. The booster antenna structure 208 has
larger turn structures than the off-chip coil and is, therefore, capable
of stronger or better coupling to the magnetic field emanating from the
antenna 204 of the reading unit 202. The booster antenna structure 208 is
coupled to the off-chip coil arranged on the chip card module 206 by
means of the at least one inductive coupling area 210, i.e. no electrical
or bodily contact is required between the circuit which has the off-chip
coil and the booster antenna structure 208. The inductive coupling area
210 can have, for example, coupling turns which surround the chip card
module 206 and thus the off-chip coil, the coupling turns being coupled
out of the turns of the booster antenna 208. Due to the spatial proximity
of the turns of the off-chip coil to the coupling turns of the booster
antenna 208, electromagnetic coupling can be achieved between the two
coils, i.e. one coil can induce currents in the other one. Other
embodiments of the at least one inductive coupling area will be explained
later.

[0039] The coupling or intensity of coupling, respectively, between a chip
card module and a booster antenna is an essential component of the
contactless performance of an overall system which essentially has the
chip card and the reading unit and can be described quantitatively by a
coupling factor or coupling parameter, respectively. The number of turns
of the booster antenna and the distance between the turns of the booster
antenna and the turns of the off-chip coil are important setting
parameters in this context, as is the size of the area of overlap of the
turns.

[0040] The effect which the booster antenna or booster antenna structure
has on the voltage induced in the chip card module antenna or in the
circuit on the chip card module by an electromagnetic field of a reading
unit is illustrated in the diagram 300 shown in FIG. 3. In the diagram
300, the number of turns of a booster antenna is plotted according to
various embodiments along the x axis 302. This number of turns can relate
to the turns which are larger than the optional coupling turns which may
enclose the at least one inductive coupling area. In the embodiment shown
in FIG. 2, the booster antenna 208 has two turns and there is an
inductive coupling area 210 which is enclosed or edged by two coupling
turns, the coupling turns being coupled out of a turn of the booster
antenna. In such embodiments, the number of turns is independent of the
number of coupling turns. Along the y axis 304, the voltage is plotted
which can be induced at the chip and/or the circuit on the chip card
module by the electromagnetic field of a reading unit located in the
vicinity of the contactless chip card module arrangement according to
various embodiments. The graph 306 in the diagram 300 illustrates that
with an increasing number of turns of the booster antenna, the induced
voltage also increases. However, the gain in voltage per additional turn
decreases with an increasing number of turns which is reflected in a rise
in the graph 306 decreasing toward greater numbers of turns.

[0041] The number of turns of the booster antenna may be limited by the
available space. In principle, the booster antenna structure may extend
to the area which is limited, for example, by the size of a chip card. In
this context, the booster antenna structure can be arranged as a layer
within the chip card, for example laminated in, considering, for example,
all sizes of chip cards which are contained in the ISO/IEC 7810 Standard.
Furthermore, process parameters, for example choice of material,
thickness of turn conductor tracks and/or geometry of the turns can be
taken into consideration in the selection of the optimum number of turns.

[0042] When designing the geometry of the booster antenna, restrictions
may occur. For example, the ISO/IEC 7811-1 Standard specifies areas for a
chip card in the ID-1 format (ID-1, as one of the chip card formats, is
specified in ISO/IEC 7810 Standard) which are not available for the
booster antenna. These may be, for example, areas for embossing and/or
the area which is covered by the chip card module. Due to these
restrictions, the design for achieving optimum coupling between chip card
module and booster antenna may be restricted. Too small a number of turns
of the booster antenna may result, for example, in suboptimal coupling.
If these boundary conditions just mentioned and also contained in the
Standard are neglected, improved coupling may be achieved but the
corresponding chip cards do not then comply with the ISO/IEC 7811-1
Standard and cannot be used, for example, where embossing plays a role.

[0043] The booster antenna structure according to various embodiments
follows the approach of estimating the areas available for the design of
the booster antenna structure, taking into consideration the respective
process parameters for producing the booster antenna structure such as,
for example, choice of material, thickness of the turn conductor tracks
and/or geometry of the turns. This makes it possible to determine an
optimum number of turns of the booster antenna.

[0044] In general, a booster antenna structure may be produced, for
example, by means of a printing process or of an etching process. In
various embodiments, the booster antenna structure can also be installed
or produced by galvanizing. Contactless systems of chip card and reading
unit can be formed in various manners but they are all subject to similar
requirements due to their application.

[0045] The electrical requirements are given by the ISO/IEC 14443
Standard, ISO/IEC 10373-6 Standard and the EMVCo Standard (EMVCo: EMV
Standard for contactless chip cards; EMV: global standard for credit and
ATM cards based on chip card technology), for example the EMV contactless
communication protocol specification version 2.0.1, July 2009. One
important requirement is the minimum operating field strength, that is to
say the minimum field strength at which a correct signal transmission can
occur between chip card and reader (and conversely). The minimum load
modulation amplitude (LMA) is also of significance. This parameter
describes a magnetic field amplitude achievable by means of the load
modulation described above, which may effect a change in the magnetic
field of the reader within the normal operating range. A further
important aspect is the maximum loading effect which relates to the
reaction of the chip card on the reader. The chip card is operated by the
electromagnetic field of the reader and, in turn, generates its own
electromagnetic field which, in turn, loads the reader. The maximum
reaction defines an upper limit for this loading effect so that the
reader can still operate correctly.

[0046] Further demands on booster antenna structures relate to their
mechanical characteristics. Thus, the booster antenna structures must be
embeddable in the chip cards, i.e. the size of the respective chip card
in which a booster antenna structure is used determines the boundaries
for a possible dimension of the booster antenna structure. Possible sizes
of chip cards may be obtained, for example, from the ISO/IEC 7810
Standard. Furthermore, the design or the shape of the booster antenna
itself may be subject to spatial restrictions within the chip card which
may result, for example, from areas to be kept free, for example for
embossed lettering as specified in the ISO/IEC 7810-11 Standard.

[0047] In this context, the production process of the booster antenna
structure may run iteratively in accordance with various embodiments.
Test models may be produced, surveyed and specified and various
parameters may be subsequently adapted for meeting the requirements.

[0048] An enlargement of the booster antenna, i.e. an enlargement of the
area enclosing the booster antenna has a positive effect on the minimum
load modulation amplitude and the minimum operating field strength since
the coupling between the reading unit and the booster antenna is
increased. At the same time, however, the reaction of the chip card on
the reading unit is increased. Generally, a size of the booster antenna
may be selected to be such as is allowed in accordance with the
corresponding restrictions or specified conditions.

[0049] In most cases, enlarging the number of turns of the booster antenna
may lead to a lower minimum operating field strength. However, this
positive effect is reduced with an increasing total number of turns
already present in the booster antenna, as can be seen in the diagram 300
in FIG. 3 (increasingly shallower graph 306 in diagram 300 in FIG. 3). At
the same time, however, the achievable minimum load modulation amplitude
is reduced with an increasing number of turns of the booster antenna. As
a compromise solution, a reasonable number of turns of the booster
antenna can be within a range of about two to about five and be, for
example, four turns in chip cards in the ID-1 format. Since the coupling
parameter or the strength of coupling between the booster antenna and the
chip card module or its antenna, respectively, may be changed without
significantly influencing other component parameters, it represents a
good parameter for aligning the entire system.

[0050] FIG. 4A to FIG. 4F show different contactless chip card module
arrangements 400, 410, 420, 430, 440, 450 according to various
embodiments for forming the inductive coupling area. In each of the
figures mentioned, a booster antenna structure 402 is shown, with only
the booster antenna being shown, and a chip card module 404 which has an
off-chip coil 406 and a chip (not shown separately). The booster antenna
402 is only shown by a line since the geometric arrangement of the
off-chip coil 406 of the chip card module 404 with respect to the booster
antenna 402 is the focal point of the explanation in FIG. 4A to FIG. 4F.
Naturally, the booster antenna structure 402 may have more than one turn,
for example two, three, four or more turns, and other components such as
capacitors or resistors. In each of FIG. 4A to FIG. 4F, the at least one
inductive coupling area is formed by the proximity of the chip card
module 404 to the booster antenna. In other words, the at least one
inductive coupling area coincides spatially with the location of the chip
card module 404. In the embodiments of the contactless chip card module
arrangement shown in FIG. 4A to FIG. 4F, the turns of the off-chip coil
406 are arranged to form an approximately square or rectangular shape
having rounded corners. In various embodiments, the sides can deviate
from a straight course (see also FIG. 1) and/or the off-chip coil 406 may
assume other geometric shapes.

[0051] In FIG. 4A, an inductive coupling between the booster antenna 402
and the off-chip coil 406 is achieved by the off-chip coil being arranged
in such a manner that two sides of the off-chip coil 406 extend over
their entire length adjoining and essentially in parallel with the turns
of the booster antenna 402. In this arrangement, the off-chip coil 406 is
arranged in an outer corner area of the booster antenna 402, i.e. in one
corner of the booster antenna 402, and outside an area which is bordered
by the turn (or turns) of the booster antenna 402 which is subsequently
called booster antenna area. Using geometries of this type, coupling
parameters of the order of magnitude of up to 0.1 can be achieved in
dependence on the number of turns of the booster antenna 402 and the
distance between these and the off-chip coil 406. The contactless chip
card module arrangement 400, shown in FIG. 4A, according to various
embodiments, may be used if an enclosure of the off-chip coil 404 by the
booster antenna 402 is not possible, for example due to areas which are
reserved for embossed lettering.

[0052] In FIG. 4B, just as in FIG. 4A, two sides of the off-chip coil 406
extend over their entire length adjoining and essentially in parallel
with parts of the booster antenna 402, but the chip card module 404 is
arranged here within the booster antenna area. In other words, the chip
card module 406 is arranged in an inner corner area of the booster
antenna 402. In comparison with the contactless chip card module
arrangement 400 shown in FIG. 4A, the contactless chip card module
arrangement 410 shown in FIG. 4B has a larger coupling parameter, i.e.
the booster antenna 402 is coupled better to the off-chip coil 406 there.

[0053] In the exemplary contactless chip card module arrangement 430 shown
in FIG. 4C, the chip card module 406 is arranged within the booster
antenna area, only one side of the chip card module 404 being arranged
immediately adjoining the booster antenna 402. Regarding FIG. 5 and the
diagram 600 shown in FIG. 6, immediately adjoining may be understood to
be a distance between a turn of the off-chip coil 406 and a turn of the
booster antenna of from up to 10 mm in various embodiments.

[0055] FIG. 4E shows a further exemplary contactless chip card module
arrangement 440 in which the booster antenna 402 is arranged immediately
adjoining and essentially in parallel with three sides of the chip card
module 404 along its complete length, the chip card module 402 being
arranged outside the booster antenna area.

[0056] By comparison, the booster antenna 402 is arranged immediately
adjoining and essentially in parallel with three sides of the chip card
module 404 along its complete length in the exemplary contactless chip
card module arrangement 450 shown in FIG. 4F, but the chip card module
404 is arranged here within the booster antenna area. In comparison with
the chip card module arrangement 440 shown in FIG. 4E, a greater coupling
parameter is obtained here. Using geometries of this type, coupling
parameters of the order of magnitude of between 0.1 and 0.2 can be
achieved in dependence on the number of turns of the booster antenna 402
and the distance between these and the off-chip coil 406.

[0057] In summary, it can be concluded from the results in FIG. 4A to FIG.
4F that, on the one hand, the arrangement of the chip card module 404
within the booster antenna area and, on the other hand, the smallest
possible distance between the off-chip coil 406 (or the turns forming the
off-chip coil 406, respectively) and the booster antenna 402 have a
positive effect on the coupling parameter, i.e. increase it. Furthermore,
the coupling factor grows with increasing number of sides of the off-chip
coil 406 which are arranged adjoining the booster antenna 402. In this
context, adjoining arrangement is understood to be an arrangement in
which the distance between the booster antenna 402 and the off-chip coil
404 is a few millimeters and is, for example, less than 4 millimeters.

[0058] As has already been found, apart from the number of turns of the
booster antenna according to various embodiments, the smallest possible
distance between the turns of the booster antenna and the turns of the
off-chip coil is also an important parameter which can influence the
coupling between booster antenna and off-chip coil. FIG. 5 shows a
section of an embodiment of an inductive coupling area 500. The coupling
area 500 is formed by a corner area of the booster antenna structure
according to various embodiments. The off-chip coil is arranged adjoining
one corner of the booster antenna, i.e. two sides of an outer turn of
turns 502 of the off-chip coil extend at a distance 506 essentially in
parallel with the turns 504 of the booster antenna. As an alternative to
the case shown in FIG. 5, the two distances 506 drawn in can also be
different.

[0059] According to various embodiments, the turn conductor tracks can
have a width in a range of approximately 50 μm up to approximately 400
μm and be, for example, about 100 μm. A turn conductor track width
in the upper range can result, for example, if the turn conductor track
acts additionally as an electrode of a plate capacitor.

[0060] In various embodiments, a booster antenna structure for a chip card
is provided, wherein the booster antenna structure has a booster antenna
and an additional electrically conductive structure connected to the
booster antenna. In various embodiments, a booster antenna may be
understood to be an amplifier antenna which supports or amplifies the
signal transmission between the chip card or the chip card module,
respectively, and a reader. In this context, the chip card module may
have a resonant circuit which may have essentially a chip card module
antenna and the chip. The booster antenna may be an inductive structure,
for example an arrangement of turns which may form, for example, a flat
coil. The coil may have, for example, a rectangular or polygonal shape or
a mixed shape of these, wherein the corners may be rounded. The
additional electrically conductive structure may be a structure
independent of the booster antenna, i.e. a structure which provides an
additional ohmic impedance to the ohmic impedance of the structures which
form the booster antenna. The booster antenna structure according to
various embodiments may be optimized, for example, with respect to its
electrical parameters and its geometry in such a manner that by this
means ISO/IEC-compliant chip cards may be provided which also meet the
EMVCo Standard.

[0061] According to various embodiments of the booster antenna structure,
the booster antenna and the additional electrically conductive structure
may jointly form an arrangement which has a resonant frequency of
approximately 13.56 MHz. In other words, the booster antenna and the
additional electrically conductive structure may form a circuit, the
resonant frequency of which is approximately 13.56 MHz. This frequency
corresponds to one of the RFID (radiofrequency identification) operating
frequencies specified according to the ISO/IEC 18000 Standard. The actual
resonant frequency may deviate from 13.56 MHz due to component
parameter-related deviations from standard parameters. In various
embodiments, a deviation of up to about 10% may be considered as
acceptable. The arrangement which has the booster antenna and the
additional electrically conductive structure can additionally have a
capacitance.

[0062] According to various embodiments of the booster antenna structure,
the additional electrically conductive structure may have a meander
structure. In various embodiments, the meander structure may have round
structures or serrated structures or structures defined by corners. The
meander structure may have, for example, a serpentine shape, wherein the
serpentine can have sections of different length between locations of
direction changes. As well, at least one corner of the meander structure
may be rounded or the meander structure may have a zigzag shape. The
meander structure may be designed overall as a periodic structure or also
have a string of periodic conductor track sections. As an alternative,
the meander structure may have a shape free of symmetry.

[0063] According to various embodiments of the booster antenna structure,
the electrically conductive structure may also be provided as a discrete
component, for example in the form of a line which has a different
material in comparison with the lines to which it is connected.
Furthermore, the electrically conductive structure may be arranged as
tapering of a line in at least one area of the booster antenna structure.

[0064] According to various embodiments of the booster antenna structure,
the additional electrically conductive structure may have, together with
the booster antenna structure, an ohmic impedance of at least 5 Ω,
for example 10 Ω, if the additional electrically conductive
structure is interconnected in series with the booster antenna. In the
case of a parallel interconnection of the additionally conductor
structure with respect to the booster antenna, the impedance of the
additionally electrically conductive structure may be, together with the
booster antenna structure, for example about 500 Ω. In serial
interconnection and in parallel interconnection, the booster antenna has
different equivalent impedances with respect to the additionally
electrically conductive structure. During the design of the booster
antenna structure, the ohmic impedance of the entire structure must be
taken into consideration, that is to say, for example, impedance of the
booster antenna, of the additionally electrically conductive structure
and, for example, of a capacitor. Compared with a direct-current
resistance, the frequency and the phase of the current or of the voltage
must be taken into consideration in the calculation of the resistance in
the case of an impedance so that the impedance can differ distinctly from
a direct-current resistance of an electronic component such as the
additional electrically conductive structure due to effects such as
self-inductance, the so-called proximity effect or the skin effect. The
actual impedance of the additionally conductive structure can be
adjusted, for example, by the choice of material and/or its shape.

[0065] According to various embodiments of the booster antenna structure,
the additional electrically conductive structure and the booster antenna
may be formed from different materials. The booster antenna can have, for
example, materials such as Ag, Al, Cu, Au or alloys thereof As well, the
additionally electrically conductive structure can have these materials,
independently of the materials selected for the booster antenna. In
general, the choice of material can be adapted taking into consideration
the shape and the dimension of the additionally electrically conductive
material so that a desired resistance value can be set.

[0066] According to various embodiments of the booster antenna structure,
the additional electrically conductive structure and the booster antenna
may be coupled to one another in series. As an alternative, according to
further various embodiments, the additional electrically conductive
structure and the booster antenna can be coupled to one another in
parallel.

[0067] According to various embodiments, the booster antenna may have at
least one inductive coupling area and be constructed as resonant circuit.
The inductive coupling area may be arranged for coupling the booster
antenna to a further antenna, for example to a chip card module antenna
arranged on a chip card module. By means of the at least one inductive
coupling area, the booster antenna may be coupled inductively to the chip
card module antenna or to the chip card module, respectively, so that no
mechanical contacts need to be provided between these two.

[0068] According to various embodiments, the booster antenna structure may
further have a capacitor. The capacitor may be connected to the booster
antenna and form in such an arrangement, together with the booster
antenna and the additionally electrically conductive structure, a
resonant circuit.

[0069] According to various embodiments of the booster antenna structure,
the capacitor may be formed as a plate capacitor. The individual
capacitor plates may be constructed on the same side or on different
sides of a foil or of a carrier on which the booster antenna structure is
arranged. Between the capacitor plates, a dielectric can also be
arranged. Generally, the capacitor may have two mutually electrically
insulated conductor strings arranged at a distance from one another,
wherein the overall structure may have any shape. Thus, the plate
capacitor may be present, for example, rolled together to form a spiral
shape, each spiral string corresponding to one of the capacitor
electrodes. The carrier or the carrier layer may have generally an
electrically insulating material, for example a plastic or a plastic
laminate, and be present as a foil or as a thin layer of material.

[0070] According to various embodiments of the booster antenna structure,
the capacitor may have a number of lines arranged next to one another in
parallel, wherein every second line is connected to the same capacitor
electrode. For example, each of the capacitor electrodes may have a
finger structure, the capacitor electrodes being rotated by 180°
with respect to one another and arranged in such a manner that at least
one finger of one capacitor electrode is arranged between two fingers of
the other capacitor electrode, the fingers of the two capacitor
electrodes being electrically insulated from one another.

[0071] According to various embodiments of the booster antenna structure,
the structures which form the capacitor, and the booster antenna
structure, may be arranged in the same plane. In this case, no additional
structural layer is required in which one of the components is arranged
separately, but both the structures forming the capacitor and the booster
antenna structure may be formed in a forming process on the same layer,
i.e. in the same plane, that is to say, for example, on one or on two
sides of the carrier on which the booster antenna structure is arranged.
The capacitor may also be configured as line capacitor and arranged, for
example, as dummy turn. The dummy turn may have two conductor tracks
extending next to one another, the winding direction of the two conductor
tracks being opposite with respect to one another so that the dummy turn
does not supply any or a negligible contribution to the inductance of the
booster antenna structure.

[0072] In various embodiments, a contactless chip card module arrangement
is provided having a booster antenna structure according to various
embodiments and a contactless chip card module which has a chip and a
coil which is electrically coupled to the chip, wherein the booster
antenna structure may be inductively coupled to the coil of the
contactless chip card module by means of at least one inductive coupling
area of the booster antenna. The inductive coupling of the coil of the
contactless chip card module with the booster antenna structure can be
achieved by positioning the coil in the vicinity of the booster antenna.
In this context, individual areas of the turns of the chip card module
coil which may have, for example, a rectangular or polygonal shape, may
extend adjoining the booster antenna on one or more sides. The chip card
module arrangement may form a part of a chip card which, for example,
meets the ISO/IEC 7810 Standard. In various embodiments, the contactless
chip card module arrangement may additionally have a contact-based
interface, for example in the form of chip card contacts arranged on the
chip card module, by means of which the contactless chip card module
arrangement can also communicate contact-based with a reading unit. Due
to the electrical or inductive coupling between booster antenna and chip
card module antenna, it is not required to form an electrical body
contact between the booster antenna and chip card module antenna which
also requires precise milling in the chip card or the chip card body,
respectively.

[0073] According to various embodiments of the contactless chip card
module arrangement, the booster antenna structure may be power-matched to
the contactless chip card module, wherein the match may be adjustable by
means of the additional electrically conductive structure. Such power
matching provides for optimum power transmission of signals or energy
between the booster antenna structure and the contactless chip card
module and can be achieved, for example, by adapting the resistance of
the additionally conductive structure to a transformed resistance of the
chip card module, the transformed resistance of the chip card module
being discussed in greater detail later.

[0074] According to various embodiments of the contactless chip card
module arrangement, the at least one inductive coupling area of the
booster antenna can have a structure enclosing the coil of the
contactless chip card module. In this context, the enclosing structure
can have an integral part of the booster antenna in the form of an output
or extension of a turn of the booster antenna which can then also form a
coil which, for example, can surround the coil of the chip card module.

[0075] According to various embodiments of the contactless chip card
module arrangement, the enclosing structure can have at least two turns
which enclose the coil of the contactless chip card module. The at last
two turns can then be arranged at an equal distance from all sides of the
coil of the chip card module. The distance between the turns of the
enclosing structure and at least one side of the coil of the chip card
module can be different, however, from the distances between the turns of
the enclosing structure and the remaining sides of the coil of the chip
card module.

[0076] According to various embodiments of the contactless chip card
module arrangement, the at least one inductive coupling area of the
booster antenna can be arranged in a corner area of the booster antenna.
The corner area of the booster antenna can have here two sides, wherein
each side can extend adjoining and essentially in parallel with one side
of the coil of the contactless chip card module.

[0077] According to various embodiments of the contactless chip card
module arrangement, the at least one inductive coupling area of the
booster antenna can be located within an area which is bounded by
conductor tracks forming the booster antenna. This can be the case, for
example, if the coil of the contactless chip card module is arranged in
an inner corner or at an inner side of the booster antenna, wherein the
inner side of the booster antenna can be specified by a turn of the
booster antenna coil which is located completely inside. The at least one
inductive coupling area can be designed in such a manner that the coil of
the contactless chip card module is surrounded essentially along three of
its sides by turns of the booster antenna and the at least one inductive
coupling area is formed as a type of bay, as it were.

[0078] According to various embodiments of the contactless chip card
module arrangement, the at least one inductive coupling area of the
booster antenna may be located outside an area which is bounded by
conductor tracks forming the booster antenna. This can be the case, for
example, if the coil of the contactless chip card module is arranged at
an outer side of the booster antenna, wherein the outer side of the
booster antenna may be specified by a turn of the booster antenna coil
which is completely located on the outside. In this context, the at least
one inductive coupling area can be formed in such a manner that the coil
of the contactless chip card module is surrounded essentially along three
of its sides by turns of the booster antenna and the at least one
inductive coupling area is formed as a type of bay, as it were.

[0079] In various embodiments, a contactless chip card module arrangement
is provided having a booster antenna structure according to various
embodiments and a contactless chip card module which has a chip and a
coil which is coupled electrically to the chip, wherein the booster
antenna structure may be coupled inductively to the coil of the
contactless chip card module and wherein the electrically conductive
structure external to the booster antenna, together with the booster
antenna structure, has an ohmic impedance, the value of which results
from an operating frequency of the chip, the inductance of the booster
antenna and the quality of the booster antenna. In this context, the
booster antenna structure may be power-matched to the contactless chip
card module. The power matching may be adjustable, for example by means
of an adaptation of the booster antenna-external electrically conductive
structure, for example a booster antenna resistance. During the
adaptation of the ohmic impedance of the booster antenna-external
electrically conductive structure, the quality of the booster antenna may
also be set and by this means the reaction of the contactless chip card
module arrangement to a reading unit can be adjusted. In various
embodiments, the booster antenna-external electrically conductive
structure may be understood to be a structure which is not a component of
the coil turns of the booster antenna but represents an electrically
conductive structure which is additional to the turns of the booster
antenna, which may be interconnected in parallel or in series with the
coil or the turns, respectively, of the booster antenna.

[0080] According to various embodiments of the contactless chip card
module arrangement, the contactless chip card module may also have chip
card contacts which are configured for providing a contact-based chip
card interface. The chip card contacts may form a contact field which
corresponds to the ISO/IEC 7816 Standard. The contact field can have six
or eight individual chip card contacts which may have normal conductive
materials.

[0081] According to various embodiments of the contactless chip card
module arrangement, the contactless chip card module arrangement may be
configured as a dual interface chip card module arrangement. The
communication with the chip of the dual interface chip card module
arrangement may then take place optionally by means of the contact-based
interface in the form of the chip card contacts or by means of the
contactless interface in the form of the chip card module antenna and the
booster antenna. A dual interface chip card may have a chip card module
which may have a chip and a coil in the form of conductor track turns
which assumes the function of an antenna and provides for the contactless
communication. The joint arrangement of the coil and of the chip on one
chip card module is also called CoM (coil on module). The interconnection
of the chip and of the coil on the chip card module of a dual interface
chip card represents a resonant circuit which may be operated
independently.

[0082] The chip card in which the booster antenna structure and/or the
contactless chip card module arrangement may be used may be, for example,
a chip card which is compliant with the ISO/IEC 7810 Standard.
Accordingly, the chip card may have each of the normal size formats ID-1,
ID-2, ID-3, ID-000 (also called mini-SIM format, SIM: Subscriber Identity
Module) or 3FF (also called micro-SIM format). Depending on the size of
the chip card, it may also have more than one chip card module. For
example, two chip card modules may be arranged on one chip card so that
the chip card may be inserted with one of its ends into a reader or
pulled through such a one and the user can thus select which chip card
module is to be used. In this case, each chip card module antenna may be
arranged in a separate inductive coupling area.

[0083] The influence of the distance between the turns 502 of the off-chip
coil and the turns 504 of the booster antenna on the strength of coupling
or the coupling parameter k, respectively, is shown in diagram 600 in
FIG. 6. The coupling parameter is plotted along the x axis 602 of diagram
600 and the distance 506 drawn in FIG. 5 is plotted along the y axis 604.
The coupling parameter may be understood in various embodiments to be a
measure in which a current flowing through particular turns (off-chip
coil or booster antenna) is capable of inducing a current flow in the
other turns (booster antenna or off-chip coil). From curve 606 in diagram
600, it may be seen that the coupling parameter k becomes ever smaller
the greater the distance 506 between the outer one of turns 502 of the
off-chip coil and the adjoining turn of turns 504 of the booster antenna.

[0084] FIG. 7 shows a section of a booster antenna structure 700 according
to various embodiments. The at least one inductive coupling area 706,
within which an off-chip coil of a chip card module may be arranged, is
formed in this case by coupling turns 704 or surrounded by these,
respectively. The coupling turns 704 may be formed by an extended turn of
the turns 702 of the booster antenna, wherein their number can be within
a range of between one and approximately five depending on the existing
space and desired strength of coupling and may be, for example, three.
Using such geometries, the highest strengths of coupling, which can be
within a range of from 0.2 to 0.3, may be achieved in dependence on the
number of coupling turns 704, the number of turns 702 of the booster
antenna and/or the distance of the turns of the off-chip coil from the
coupling turns. The case may also occur in which an overlap can occur
between the chip card module antenna of the chip card module and the
booster antenna on at least one of the sides if, for example, the area of
the chip card module antenna is greater than the inductive coupling area
which is fixed by the coupling turns 704.

[0085] Further embodiments of the at least one inductive coupling area are
shown in each case in FIG. 8A and FIG. 8B. In both figures, a section of
a contactless chip card module arrangement 800 according to various
embodiments is shown which has the at least one inductive coupling area
806. Within the at least one inductive coupling area 806, the chip card
module 804 is arranged on which the chip 810 surrounded by the off-chip
coil 808 is located. The at least one inductive coupling area 806 is
formed by parts of the booster antenna 802 both in FIG. 8A and in FIG.
8B. In both figures, booster antenna 802 is shown simplified by only one
turn; naturally, there can be further turns. As in FIG. 7, for example,
the inner turn can have a part-piece which is constructed to form a small
coil in the form of small turns which border the at least one inductive
coupling area 804 as shown in FIG. 8A and in FIG. 8B, wherein the turns
enclosing the at least one inductive coupling area 804, in deviation from
the presentation in the figures, also have rounded corners and/or have a
round, oval or polygonal shape. The distance between each of the sides of
the chip card module 806 or the off-chip coil, respectively, from the
sides of the inner turn of the at least one inductive coupling area 806
can be different for at least one of the sides. In other words, the chip
card module 804 does not need to be arranged centrally or symmetrically
within the at least one inductive coupling area 806. In FIG. 8A and in
FIG. 8B, the arrows show a possible direction of current flow within the
booster antenna 802. In the embodiment shown in FIG. 8A of the booster
antenna structure 800, the direction of current flow within the booster
antenna 802 or within its turns, respectively, matches the direction of
current flow within the smaller turns enclosing the at least one
inductive coupling area 804. In other words, the direction of the
electromagnetic field which is generated by current flow through the
turns of the booster antenna 802 without taking into consideration the at
least one inductive coupling area 806 matches the direction of the
electromagnetic field which is generated by the current flow through the
smaller turns enclosing the at least one inductive coupling area 806. In
the embodiment shown in FIG. 8B of the booster antenna structure 800, the
direction of current flow within the booster antenna 802 or within its
turns, respectively, does not match the direction of current flow within
the smaller turns enclosing the at least one inductive coupling area 804,
the directions of current flow are opposite one another in this case. In
other words, the direction of the electromagnetic field which is
generated by current flow through the turns of the booster antenna 802
without taking into consideration the at least one inductive coupling
area 806 is arranged opposite the direction of the electromagnetic field
which is generated by current flow through the smaller turns enclosing
the at least one inductive coupling area 806. Furthermore, it must be
noted that both alternatives provide good inductive coupling of the
booster antenna 802 with the chip card module 804 or the off-chip coil
808, respectively.

[0086] In the case of the embodiments of the booster antenna structure,
shown in FIG. 8A and in FIG. 8B, the sensitivity of the accuracy of
positioning of the chip card module 804 within the at least one inductive
coupling area 806 has been investigated. As a result, it has been
determined that deviations of up to about 1.5 mm of the chip card module
in one of the three spatial directions from its specified position can
scarcely be detected, that is to say system variables such as response
field strength or load modulation amplitude change only insignificantly.
From a deviation of about 2 mm of the chip card module in one of the
three spatial directions from its predetermined position, changes can be
detected which, however, still provide for correct operation of the
contactless chip card module arrangement. Overall, it can be concluded
from this that the contactless chip card module arrangement according to
various embodiments is insensitive to displacements or positioning errors
of the chip card module with respect to the booster antenna structure
which can considerably simplify the production of a corresponding chip
card which can have the contactless chip card module arrangement
according to various embodiments.

[0087] FIG. 9 shows a circuit diagram 900 of a system having a reading
unit 902 (also called PCD (proximity coupling device)) and a contactless
chip card module arrangement 904 (also called PICC (proximity integrated
circuit card)) according to various embodiments. The reading unit 902 has
a reading unit antenna 910 which can be formed as a coil. The contactless
chip card module arrangement 904 which, for example, can be part of a
contactless chip card or of a dual interface chip card has a chip card
module 908 and a booster antenna structure 906. The chip card module 908
has an off-chip coil 918 which is connected to the chip which is modeled
by a parallel circuit of an on-chip capacitor 920 and an on-chip resistor
922, the latter representing the ohmic consumption of the chip. The
on-chip capacitor 920 can also represent a (parasitic) capacitor,
connected in parallel with the on-chip coil 918, of the chip card module
antenna and/or an off-chip capacitor. In addition, a further resistor can
be connected in series with the off-chip coil 918. The booster antenna
structure 906 is represented by a resonant circuit in the form of a
series circuit which has a booster antenna coil 912, a booster capacitor
914 and an additional electrically conductive structure, for example a
booster resistor 916. In the circuit of the booster antenna structure
906, the booster resistor 916 may also be connected alternatively in
parallel with the arrangement which has the booster antenna coil 912 and
the booster capacitor 914. The three part-systems may be coupled
electromagnetically to one another. A first arrow 926 identifies the
electromagnetic coupling between the booster antenna structure 906 and
the off-chip coil of the chip card module 908, the second arrow 924
identifies the electromagnetic coupling between the booster antenna
structure 906 and the reading unit 902 and a third arrow 928 identifies
the electromagnetic coupling between the reading unit 902 and the
off-chip coil 918 of the chip card module 908.

[0088] One of the aims in designing the booster antenna structure can
consist in reducing the reaction effect below a certain limit which can
be given, for example, by the ISO/IEC 10373-6 Standard or by the EMV
contactless communication protocol specification 2.0.1, without
increasing the required minimum operating field strength in doing so. The
reaction effect may be reduced, for example, by reducing the quality
factor of the booster antenna which results from the product of the
operating frequency and the inductance of the booster antenna coil 912
divided by the booster resistance 916. The reduction in the quality
factor can be achieved by increasing the booster resistance 916 and a
further resistance which results from a transformation of the chip card
module circuit 908 into the booster antenna structure circuit 906 due to
the electromagnetic coupling between booster antenna 912 and the off-chip
coil 918. In the case where the resonant frequency of the resonant
circuit which has the chip card module antenna and the chip, corresponds
to the operating frequency, this transformed resistance of the chip card
module RMtr is obtained as

R Mtr = R IC k BM 2 L B L M , ##EQU00001##

[0089] where RIC corresponds to the on-chip resistance 922, kBM
corresponds to the strength of coupling 926 between the booster antenna
structure 906 and the off-chip coil 918, LB corresponds to the
inductance of the booster antenna coil 912 and LM corresponds to the
inductance of the off-chip coil 918. A normal on-chip resistance RIC
can be, for example, 1 kiloohm, a normal inductance of the off-chip coil
can be, for example, 2.4 microHenry.

[0090] The sum of the booster resistance 816 and the transformed
resistance of the chip card module RMtr corresponds to a total
resistance Rtotal which determines the reaction effect. In the case
of chip cards in the ID-1 format (according to ISO/IEC 7810 Standard),
the total resistance Rtotal can be, for example, approximately 65
ohms. To achieve power matching between the chip card module and the
booster antenna structure, the transformed resistance of the chip card
module RMtr and the booster resistance 916 can be selected to be
approximately equal. This makes it possible that an optimum of power can
be transferred between chip card module and booster antenna. The booster
resistance 916 can be adapted, for example, via the width of the turn
conductor tracks of the booster antenna 912 and/or by means of a suitable
choice of the total length of the booster antenna 912 without the
inductance of the booster antenna 912 and the booster antenna area, i.e.
the area which is bordered by the booster antenna turns, being changed
significantly.

[0091] The aspect of power matching between chip card module and booster
antenna is clarified by means of FIG. 10 which shows an equivalent
circuit diagram of a contactless chip card module arrangement 1000 having
a chip card module antenna, a chip and a booster antenna according to
various embodiments. A reading unit can induce in the booster antenna a
voltage which is shown as voltage source 1002 in the equivalent circuit
diagram of the contactless chip card module arrangement 1000. The voltage
source 1002 has a voltage generator 1006 which represents the induced
voltage, and an internal impedance 1008 which takes into consideration
the ohmic resistance of the booster antenna structure. The inductive
coupling between booster antenna and chip card module antenna within the
contactless chip card module arrangement 1000 according to various
embodiments is taken into consideration here by means of an equivalent T
circuit which has a first inductance 1014 (MBM), a second inductance
1012 (LB-MBM) and a third inductance 1016 (LM -MBM).
The contactless chip card module arrangement 1000 which can be, for
example, a part of a contactless chip card or of a dual interface chip
card, has a chip card module and a booster antenna structure which are
shown as one unit for simplification in the circuit diagram in FIG. 10.
The chip card module has an off-chip coil which is represented in the
third inductance 1016 which is connected to the chip which is modeled by
means of a parallel circuit of an on-chip capacitance 1018 and an on-chip
resistance 1020. The booster antenna structure is modeled by a series
circuit which has a booster antenna coil which is represented in the
second inductance 1012, the resistance 1008 and a booster capacitance
1010.

[0092] Normal chip card systems with inductive coupling between a chip
card module and a booster antenna do not meet the requirements of
relevant performance standards for chip cards such as EMVCo and/or
ISO/IEC 10373-6. One possibility of solving this problem consists in
optimizing the power transfer by selectively matching the booster antenna
to the chip card module which has the chip card module antenna and the
chip.

[0093] Optimizing the power transfer can involve a number of aspects. On
the one hand, the resonant chip card module circuit (e.g. see chip card
module circuit 908 in FIG. 9), which essentially has the chip and the
off-chip coil, can be set to the operating frequency of the chip for this
purpose which can be, for example, at 13.56 MHz. The resonant frequency
of the resonant chip card module circuit can be adjusted, for example, by
means of adapting the inductance of the off-chip coil and/or by providing
an additional off-chip capacitance. On the other hand, the resonant
frequency of the booster antenna circuit (e.g., see booster antenna
circuit 906 in FIG. 9) can also be set to the operating frequency of the
chip, that is to say, for example, to 13.56 MHz. The resonant frequency
of the booster antenna circuit can be adjusted, for example, by means of
the additional electrically conductive structure connected to the booster
antenna or by means of a capacitance. Furthermore, the quality factor of
the booster antenna can be determined and adapted by means of the
additionally electrically conductive structure (e.g. booster resistance
916 in FIG. 9) in such a manner that it corresponds to the real component
of a complex impedance (see complex impedance Z in FIG. 10) which
corresponds to the electrical impedance which is produced by introducing
a chip card with a contactless chip card module arrangement into the
electromagnetic field of the antenna of the reading unit in its circuit.
In other words, by adjusting the quality factor of the booster antenna,
for example by means of the additionally electrically conductive
structure, the reaction effect of the booster antenna structure on the
reading unit can be adjusted so that a maximum standardized effect of
reaction on the reading unit or the antenna of the reading unit,
respectively, is not exceeded. At the same time, the power matching
between the booster antenna and the chip card module or the off-chip
coil, respectively, provides for operation at a working field strength
required as standard. Overall, it is possible to say that the booster
antenna structure can be adapted individually for various chip cards as a
result of which relevant standards for contactless systems can be met.

[0094] As already mentioned, a capacitor may be provided in the booster
antenna structure for adjusting the resonant frequency of the booster
antenna which can lie, for example, at 13.56 MHz. The capacitor may be
produced in various ways. If both surfaces of the layer are available in
which or on which the booster antenna structure is formed (called carrier
layer in the text which follows), the capacitor may be formed, for
example, in the form of a plate capacitor, where one plate each can be
arranged on one surface in each case. If the capacitor is to be formed on
only one of the surfaces, capacitors may be provided which have conductor
tracks extending adjacent to one another which have, for example, a
finger structure or a spiral structure. In each case, the required
capacitance value CB of the capacitor may be calculated as follows:

C B = 1 ( 2 π f res ) 2 L B ,
##EQU00002##

[0095] where fres is the resonant frequency of the circuit and
LB is the inductance of the booster antenna.

[0096] The capacitance C of plate capacitors in which the capacitor plates
are arranged on different sides of the carrier layer is obtained, on the
one hand, from the area A of one of the plates or electrodes of the
capacitor and, on the other hand, from the thickness d and the dielectric
conductivity c of the layer or of the substrate on which the booster
antenna is arranged:

C = A d . ##EQU00003##

[0097] FIG. 11A shows a possible embodiment of a capacitance 1104 of the
booster antenna structure 1100 which has a finger shape (finger capacitor
in the text which follows) and is connected in series with the booster
antenna 1102, the booster antenna 1102 being represented here by only one
turn, by way of example. An enlarged view of the finger capacitor 1104 is
shown in FIG. 11B. The finger capacitor 1104 has a first electrode 1106
and a second electrode 1108 which in each case have a comb-like or
finger-like structure and form a so-called interdigital structure. In
other words, the electrodes have a number of conductor tracks extending
in parallel next to one another, one conductor track of the other
electrode being arranged in each case between two conductor tracks each
of one electrode. The capacitance may be adjusted, for example, by means
of a suitable number of the conductor track fingers per electrode and/or
the proportion by which the fingers of the two electrodes overlap or are
pushed into one another and/or the size of the free spaces between the
fingers of an electrode and/or by providing a dielectric material between
the fingers and/or the dimension of the conductor tracks forming the
fingers, i.e. the dimension of the cross sectional area of the conductor
tracks forming the fingers.

[0098] A further possible form which the capacitance can have is shown in
FIG. 12A. To illustrate, the booster antenna structure 1200 is here also
represented by only one turn 1202 and connected to a spiral capacitor
1204. A spiral capacitor 1204 may be understood in various embodiments to
be a capacitor which has two conductor tracks forming a conductor track
string and extending next to one another, the conductor track string
being rolled together to form a spiral. In this arrangement, the spiral
does not need to have a circular shape, it can also be oval or a polygon
having rounded corners. The capacitance value of the spiral capacitor is
adjustable, for example by adapting parameters which have already been
mentioned in conjunction with the finger capacitor.

[0099] Another further possible shape which the capacitance can have is
shown in FIG. 12B. The booster antenna structure 1210 has three turns
1212 in this case. Furthermore, the end of the inner turn of the turns
1212 of the booster antenna structure 1210 is followed by an inductive
coupling area 1216 which is surrounded by coupling turns 1218. The, for
example, three coupling turns 1218 are here formed from an extension of
one end of an inner turn of the turns 1212 of the booster antenna
structure 1210. The end of the conductor track formed by the coupling
turns 1218 is followed by a dummy turn 1214 which forms the capacitor.
The dummy turn 1214 has two conductor tracks extending in parallel next
to one another, the first conductor track 1220 being coupled to the end
of the conductor track which forms the coupling turns 1218 and the second
conductor track 1222 being coupled to the end of the outer turn of the
turns 1212 of the booster antenna structure 1210. The first conductor
track 1220 and the second conductor track 1222 have an opposite direction
of circulation with respect to one another. The ends of the first
conductor track 1220 and of the second conductor track 1222 are open or
are not connected to any other structure analogously to the end of the
conductor track double string which forms the spiral capacitance 1204 in
FIG. 12A. The double string which is formed by the first conductor track
1220 and the second conductor track 1222 as such has two turns, wherein
its course can deviate from the course shown in FIG. 12B and can be
matched to unoccupied areas in the plane of the booster antenna structure
1210 or to areas to be kept free which, for example, are reserved for
embossed lettering.

[0100] FIG. 13A shows an embodiment of a front or top 1300 and FIG. 13B
shows an embodiment of a bottom or rear 1320 of a booster antenna
structure. The embodiment is based on a two-sided design, i.e. a design
formed on both surfaces of the carrier layer 1310 on which the booster
antenna structure is arranged. The embodiment shown in FIG. 13B and FIG.
13B of a booster antenna structure may be produced, for example, by
printing conductive structures on the substrate 1310 or by means of
electroplating, but analogous structures may also be produced by means of
an etching process. On the basis of the considerations presented here, an
antenna booster structure according to various embodiments or a
contactless chip card module arrangement according to various embodiments
may be produced cost-effectively which meets the ISO/IEC 14443 Standard
and/or the ISO/IEC 10373-6 Standard and/or the EMVCo Standard, taking
note of the areas reserved for embossing.

[0101] The embodiment of a booster antenna structure shown in FIG. 13A and
FIG. 13B may have a carrier layer or a carrier substrate 1310 which can
have, for example, PVC. The substrate 1310 can have the size of a chip
card in ID-1 format (80 mm×48 mm) The structures arranged thereon
can be distributed in such a manner that areas which are provided, for
example, for embossing on the chip card, are kept free. In this
embodiment, the booster antenna 1302 has two turns--one on the front and
one on the rear of the carrier layer 1310, each of these turns extending
close to the edge of the carrier layer 1310 in order to be extended
essentially over the entire size of a chip card. The turn on the front
1300 of the booster antenna structure is connected to the turn on the
rear 1320 of the booster antenna structure by means of through-contacting
1312. Apart from the two main turns, the booster antenna has additionally
two coupling turns 1308 which are also arranged on both sides of the
carrier layer 1310 and surround the at least one inductive coupling area
1304. In the embodiment shown in FIG. 13A to FIG. 13C, the
through-contacting 1312 connects the ends of the coupling turns 1308 to
one another through the carrier layer 1310, these ends being connected in
each case on the front 1300 and the rear 1320 of the booster antenna
structure to one end of the turn of the booster antenna 1302. The way in
which the coupling area 1304 is formed corresponds essentially to the
principle already shown in conjunction with, for example, FIG. 7.
Furthermore, an electrode of a plate capacitor 1306 is arranged on each
surface of the carrier layer 1310. The electrodes are arranged above one
another on the different sides or surfaces of the carrier layer 1310 and
have essentially a distance from one another which corresponds to the
thickness of the substrate 1310. With an inductance of the booster
antenna coil 1302 of, for example, two microHenry, the coupling parameter
between the off-chip coil (not shown) and the booster antenna 1302 may be
approximately 0.2. The total resistance Rtotal may be 65 Ohms so
that both the booster resistance and the transformed resistance of the
chip card module RMtr should be approximately 32 ohms for the
purpose of power matching. Furthermore, an electrically conductive
structure 1314 which has a meander shape is coupled to one another in
series with the coupling turns 1308 within the booster antenna structure.
In this embodiment, the first additional electrically conductive
structure 1314 is arranged on the front 1300 of the booster antenna
structure. As an alternative, it may also be arranged on the rear 1302 of
the booster antenna structure.

[0103] In order to provide a correspondingly dimensioned additionally
electrically conductive structure in the form of the booster resistor, a
technology can be selected for its production which normally exhibits a
higher resistance in conjunction with small conductor track widths such
as, for instance, a printing process in which functional electronic
materials present in liquid or pasty form may be printed onto the carrier
layer 1310. Furthermore, the conductor track width and the conductor
track thickness, that is to say the conductor track cross section, can be
reduced until the desired resistance value is achieved. The length of the
booster antenna or its turns, respectively, can also be extended in such
a manner that the other parameters of the booster antenna, for example
the inductance of the booster antenna, are not significantly changed. In
the embodiment of the booster antenna structure shown in FIG. 13A and
FIG. 13B, the thickness of its conductor tracks can be 5 μm and the
width of its conductor tracks can be 100 μm in order to achieve a
resistance value of about 32 ohms when using an etching technique with
copper as the conductive material. The precise parameters may be
determined by accurate measurement of the resistance and/or the effect of
reaction on a reading unit. The resonant frequency may be adjusted in a
simple manner, for example by trimming the plates of the capacitor 1306
with a cutting tool until the desired resonant frequency of, for example,
13.56 MHz is reached.

[0104] The booster antenna structure according to various embodiments can
be formed by means of various production methods. However, various
production methods have a different effect on electrical characteristics
of the booster antenna structure. This means that it may be necessary to
produce a separate design for each of the different production methods in
order to produce a particular booster antenna structure according to
various embodiments. In other words, a booster antenna structure which is
identical with respect to operating parameters can be formed from various
designs since different production methods have different effects on
electrical characteristics of electrical structures. Furthermore, it
should also be taken into consideration that in designing the booster
antenna structure for a chip card in ID-1 format, certain areas are not
available for the booster antenna structure such as, for instance, a chip
cavity into which the chip card module is inserted and/or areas which are
reserved for embossing according to the ISO/IEC 7811-1 Standard.

[0105] Booster antennas are available which are constructed in printed
form. The design does not take into consideration the areas to be kept
free and it is questionable how it can be transferred to other production
methods, if at all.

[0106] It is possible to investigate the different effect of different
production methods on the electrical characteristics of a booster antenna
structure. In this context, electrical components of the booster antenna
structure such as, for instance, capacitive and/or inductive structures
and/or the additionally electrically conductive structure can be matched
to the material and process characteristics of different production
methods in the equivalent circuit diagram. By understanding the influence
of various production methods on electrical characteristics of the
booster antenna structure, prefabricated booster antenna structure
templates (inlay structures) of various manufacturers can be utilized, on
the one hand. On the other hand, the performance of the booster antenna
structure according to various embodiments, and the yield in the
production, can be optimized.

[0107] In the text which follows, specific design criteria are explained
for various production methods. It is possible to define equivalent
circuit diagram parameters for each equivalent circuit diagram of an
electrical structure in the booster antenna circuit depending on the
production technology used.

[0108] In a production method which is effected by laying at least one
conductive conductor (wired technology), conductive structures of a wire
can be arranged on a substrate surface or carrier layer surface,
respectively, wherein normal conductive materials such as copper, silver,
aluminum, gold can be used as conductors. In this production method,
resistances, for instance the resistance of the additionally electrically
conductive structure of the booster antenna according to various
embodiments can be adjusted by a suitable choice of the material and the
diameter of a conductor used for the wiring. Furthermore, the conductor
track length can also be adapted by forming, for example, meander-shaped
wiring passages. Inductive structures can be produced by means of
conductor tracks extending adjacently to one another, wherein the value
of the inductance can be adjusted via their distance from one another.
Inductive structures can have, for example, turns, wherein the value of
the inductance can be adjusted by means of their number and size of the
area bordered by them. Capacitive structures can be produced by line
capacitances, for example in finger form or in spiral form. Furthermore,
a capacitive structure can result in conjunction with a meander shape of
the additional electrically conductive element.

[0109] In a production of the booster antenna structure by means of an
etching process or of an electroplating printing process in which the
basic electrical structures are initially printed on and then formed by
means of an electroplating process, the resistance, for instance the
resistance of the additionally electrically conductive structure of the
booster antenna structure according to various embodiments, can be
adjusted by the thickness and width of the conductor track, that is to
say its cross section, and by the material used. Similarly,
meander-shaped structures can be formed for increasing the conductor
track length and thus the resistance. Inductive structures can be
produced by means of conductor tracks extending adjacently to one
another, wherein the value of the inductance can be adjusted via their
distance from one another. For example, inductive structures can have
turns, wherein the value of the inductance can be adjusted by their
number and the size of the area bordered by them. Capacitive structures
can be provided by a plate capacitance. For this purpose, separately
formed capacitor electrodes in the form of plates can be formed, for
example, on the front and rear of the carrier substrate on which the
booster antenna is formed. Similarly, capacitive structures can be formed
in the form of conductor tracks of the turns of the booster antenna
arranged above one another on the front and rear of the carrier
substrate. Furthermore, single-layer capacitive structures, that is to
say formed only on one of the surfaces of the carrier substrate, can be
provided, for example in finger form or in spiral form. A capacitive
structure can also be formed in conjunction with a meander form of the
additional electrically conductive element.

[0110] FIG. 14 shows an embodiment of a booster antenna structure 1400
according to various embodiments which can be produced by means of an
electroplating printing process. The booster antenna structure 1400 can
be arranged on a carrier substrate 1410 which can have, for example, PVC
and is provided with conductive structures on both sides. The carrier
substrate 1410 can have the size of a chip card in ID-1 format. One turn
each of the booster antenna 1402 is arranged extending along the edge of
the carrier substrate 1410 on the front and on the rear of the carrier
substrate 1410. Apart from these main turns, the booster antenna 1402
additionally has smaller coupling turns which are also arranged on both
sides of the carrier substrate 1410 and enclose the at least one
inductive coupling area 1404. Furthermore, a first electrode of a first
plate capacitor 1406 and a first electrode of a second plate capacitor
1408 is arranged on each surface of the carrier substrate 1410. A
corresponding second electrode of the first plate capacitor 1406 and a
corresponding second electrode of the second plate capacitor 1408 is
arranged on the other side of the carrier substrate 1410--the carrier
substrate 1410 acts here as a spacer between the two electrodes of the
plate capacitors. If necessary, the carrier substrate 1410 can be thinned
down at the locations of the plate capacitors if a distance is required
between the capacitor plates of the first plate capacitor 1406 and/or the
second plate capacitor 1408 which is smaller than the thickness of the
carrier substrate 1410. Furthermore, an additional electrically
conductive structure 1412 is arranged on the carrier substrate 1410 which
is connected to the booster antenna structure 1400. The additional
electrically conductive structure 1412 has a meander form wherein
differently long meander areas can be contained within an additionally
electrically conductive structure 1412. The electrical structures on both
surfaces of the substrate 1410 are in electrical contact with one another
by means of feed-throughs 1414.

[0111] FIG. 15 shows an embodiment of a booster antenna structure 1500
according to various embodiments which may be produced by means of an
etching process. The exemplary booster antenna structure 1500 shown in
FIG. 15 is similar to the exemplary booster antenna structure 1400 shown
in FIG. 14 so that corresponding structures carry the same reference
symbols. Due to an etching process used for the production, however, the
booster antenna structure 1500 has a more filigree design compared with
the booster antenna structure 1400 which may be produced by means of
electroplating printing processes.

[0112] A further possibility for producing a booster antenna structure
according to various embodiments consists in using a printing process in
which the basic electrical structures are completely printed on. The
resistance, for instance the resistance of the additionally electrically
conductive structure of the booster antenna according to various
embodiments can be adjusted in this production process by the thickness
and width of the conductor track, that is to say its cross section, and
by the material used. Similarly, meander-shaped structures can be formed
for increasing the conductor track length and thus the resistance.
Furthermore, a separate resistance element may be provided by using a
different material which can be used for printing at one location in the
circuit of the booster antenna structure. Inductive structures may be
produced by conductor tracks extending next to one another, wherein the
value of the inductance may be adjusted by their distance from one
another. Inductive structures can have turns, for example, wherein the
value of the inductance can be adjusted by their number and the size of
the area bordered by them. Capacitive structures can be provided by a
plate capacitors. For this purpose, separately formed capacitor
electrodes in the form of plates, for example, may be formed on the front
and rear of the carrier substrate on which the booster antenna is formed.
Similarly, capacitive structures in the form of conductor tracks of the
turns of the booster antenna arranged above one another on the front and
rear of the carrier substrate may be formed. Furthermore, single-layer
capacitive structures, i.e. formed only on one of the surfaces of the
carrier substrate, may also be provided, for example in the form of
fingers or in spiral form. A capacitive structure can also be formed in
conjunction with a meander-form of the additional electrically conductive
element.

[0113] While the invention has been particularly shown and described with
reference to specific embodiments, it should be understood by those
skilled in the art that various changes in form and detail may be made
therein without departing from the spirit and scope of the invention as
defined by the appended claims. The scope of the invention is thus
indicated by the appended claims and all changes which come within the
meaning and range of equivalency of the claims are therefore intended to
be embraced.